X-ray computed microtomography (XCMT) has been applied to ceramic samples of different materials to visualise, for the first time at this scale, real 3D microstructural evolutions during sintering. Using this technique, it has been possible to follow the whole sintering process of the same grains set. Two materials have been studied; a glass powder heat treated at 700 C and a crystallised lithium borate (Li6Gd(BO3)3) powder heat treated at 720 C. XCMT measurements have been done after different sintering times. For each material, a sub-volume was individualised and localised on the successive recordings and its 3D images numerically reconstructed. Description of the three-dimensional microstructures evolution is proposed. From the 3D experimental data, quantitative evolutions of parameters such as porosity and neck size are presented for the glass sample. Possibilities offered by this technique to study complex sintering processes, as for lithium borate, are illustrated.

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The mixed valence spinel Lil+xTi2-x04 (0 2 x 2 0.33) compounds are superconducting for x s 0.12 (T,,,, = 12.7 K) and present a metal or semiconductor-like transition for x = 0.2. In order to study the context of such interesting electronic properties, we performed Ti Kedge measurements in these compounds and in the related systems MgTi204 and TiO,.The evolution of the intensity, position and shape of the pre-edge and main edge features is reported. We show that these data do not support a one-electron description and suggest that LiTi204 is a correlated d electron metal ( U Modifications in the pre-edge spectra as a function of temperature have been observed for LiTi,O,, Lil.33Ti, 6704 and Ti02. We discuss possible interpretations of this effect (vibronic coupling or thermally induced lattice deformation).

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The constant increase in power and heat flux densities encountered in electronic devices fuels a rising demand for lightweight heat sink materials with suitable thermal properties. In this study, discontinuous pitch-based carbon fiber reinforced aluminum matrix (Al-CF) composites with aluminum-silicon alloy (Al-Si) were fabricated through hot pressing. The small amount of Al-Si contributed to enhance the sintering process in order to achieve fully dense Al-CF composites. A thermal conductivity and CTE of 258 W/(m K) and 7.0 9 10 -6 /K in the in-plane direction of the carbon fibers were obtained for a (Al 95 vol% ? Al-Si 5 vol% )-CF 50 vol% composite. Carbon fiber provides the reducing of CTE while the conservation of thermal conductivity and weight of Al. The achieved CTEs satisfy the standard requirements for a heat sink material, which furthermore possess a specific thermal conductivity of 109 W cm 3 /(m K g). This simple process allows the low-cost fabrication of Al-CF composite, which is applicable for a lightweight heat sink material.